1. Evolution
Evidence from the past

2. Study of fossils Systematic study of all fossils==paleontology
Fossil record consists of over 250,000 species of which <1% are living today
Started in 18th century with Baron Georges Cuvier

3. Cuvier
Notably revealed that most fossils were of extinct species and each layer of earth contained distinct species.
Contrary to times==all fossils are from living species
Simple organisms found at all layers but only the more complex were found at shallow depths
Many species only found at one depth

4. Catastrophism
Theory of Cuvier’s, that proposed global catastrophes caused widespread extinctions which gave way to newly created species
Any problems with this?
While it accounted for species only being found at one depth, it could not account for the increase in complexity at shallower depths.

5. Cuvier's terms Coined relative age and absolute age of fossil deposits
Relative age: estimate of the age of a fossil by comparing it to other fossil specimens (according to depth)
Absolute age : an actual estimate of the age of a fossil specimen (did not have means to do this at the time)

6. How old is the earth? Any guesses? Approximately 4.6 billion years old
Scientists dated meteorites and used a method known as radiometric dating
It involves Radioisotopes: atoms that undergo radioactive decay due to an unstable nuclear arrangement, which can be measured with a high degree of accuracy.

7. Radiometric dating
Radioisotopes decay at a constant rate known as a half-life.
The half-life is the time it takes for 50% of a parent isotope to turn into a daughter isotope.
It is important to note that they are unaffected by temperature, moisture and various other environmental conditions, which makes it efficient.

8. Radiometric dating tools
Some of the Primary Radiometric Dating Methods
Parent
Daughter
Half Life(years)
Dating Range(years)
Items Typically Dated
Uranium-238
Lead-206
4.5 billion
Greater than 10 million
Zircon, Uraninite.
Uranium-235
Lead-207
704 million
Potassium-40
Argon-40
1.3 billion
Greater than 100,000
Muscovite, Biotite, volcanic rocks.
Rubidium-87
Strontium-87
49 billion
Muscovite, Biotite, Metamorphic or Igneous rocks.
Carbon-14
Nitrogen-14
5,730
,000
Wood, Charcoal, Peat, Bone, Tissue,

9. Dating fossils
Uses carbon-14 which has a half-life at 5730 years

10. Pre-darwinian ideas
We know from last day that the fossil record provides evidence to the evolutionary puzzle. Geologists added the next piece…
In 1795 James Hutton proposed the theory of actualism, which contrasted Cuvier.
Actualism: a theory stating that the same geological processes occurring today also occurred in the past.

11. Pre-darwinian ideas
In 1830 Sir Charles Lyell extended upon actualism, which his theory of uniformatarianism.
This is the theory that the earth has and will always be undergoing a gradual, uniform, and constant state of change==same intensity as now.
Conclusions from Lyell and Hutton:
The earth must be incredibly old
Dramatic extreme change could occur at what would seem to be a slow pace

12. Other key players
Buffon: species could change over time, leading to new organisms
Linnaeus: a few species have produced many new species through hybridization and interbreeding
Grandpa Darwin: first detailed writings of evolution==everything arose from one source

13. Other key players de Lamarck: Environment key role in evolution
Species must have the ability to adapt to changing conditions
Did not believe in a single origin of life; instead species gradually become more complex
Spontaneous generation==living organisms arise from non-living matter
Acquired traits==changes in an individual as a result of interactions with the environment
These changes could be inherited
WRONG!!! Acquired traits cannot be inherited
This paved the way for Charles Darwin

14. Pgs 513-518 Work: PP’s pg 515 End of Unit Project
Reading
Pgs Work: PP’s pg 515 End of Unit Project
For next class perhaps…debate regarding fossils: should fossils be donated or auctioned? And/or activity page 534 of text